Ocean color remote sensing without explicit aerosol correction

After correction of molecular scattering satellite radiance in the visible and near infrared may be linearly combined to retrieve surface chlorophyll abundance directly without explicit correction of aerosol scattering and absorption. The coefficients minimize the perturbing effects, which are modeled by a polynomial, and do not depend on geometry. The technique is developed for Global Imager (GLI) spectral bands centered at 443, 565, 667, and 866 run, but is applicable to other sets of spectral bands. A wide range of geophysical and angular conditions is considered. Using a polynomial with exponents -2, -1, and 0 to determine the coefficients, the residual influence of the atmosphere on the linear combination is small compared with the corrected satellite radiance, generally within +/-0.001, except at large view and sun angles, where it may reach 0.005 in magnitude. The resulting root mean squared (rms) error on chlorophyll abundance is 8.4%. Application of the method to GLI simulated imagery shows that estimated and actual chlorophyll abundance are in agreement, with an average rms difference of 32.1% and an average bias of -2.2% (slightly lower estimated values). The advantage of the method resides in its simplicity and rapidity of execution. Knowledge of aerosol amount and type is avoided. There is no need for look-up tables of aerosol optical properties. However, accuracy depends on the bio-optical model selected to relate the linear combination to chlorophyll abundance, which may vary depending on water type or biological province.